One of the main drawbacks with the use of finite control set model predictive control (FCS-MPC) in power converters is the variable switching frequency. When not taken into consideration, it can vary randomly depending mainly on the operating point of the system and the sampling time. This will produce a wide distributed voltage and current spectrum, causing audible noise, resonances, and poor steady-state behavior. To address this issue, a new algorithm, based on the control of the switching period within the cost function, is proposed in this paper. The algorithm shows to be very effective in achieving a regular commutation pattern, similar to pulse width modulation (PWM) techniques, which is evidenced even by similarities in the sideband harmonics generated in the voltage spectrum. The algorithm is easy to design and implement, demanding very low computation power, and enables a combination of the advantages of FCS-MPC with the benefits of a PWM-like power quality. Simulations and experimental results are presented to validate the proposed method, which are compared to previously reported FCS-MPC techniques dealing with the same challenge.

Switching Frequency Regulation for FCS-MPC Based on a Period Control Approach

Model-based predictive control techniques, with finite set control, are considered an interesting option to control multiphase drives due to their control flexibility and fast dynamic response. However, those techniques have some drawbacks such as a high computational cost, poor ( $x-y$ ) currents reduction, and steady-state error, especially at high speeds. To improve some of these drawbacks, modulation stages have been presented as an alternative. However, some of those drawbacks have not been improved. This article proposes a novel approach to the classic predictive current control (PCC) applied to an asymmetrical six-phase induction machine, where a space vector modulation with specific vectors is used in order to improve the ( $x-y$ ) currents, the steady-state error and total harmonic distortion (THD) at high operation speeds. Experimental results are presented to demonstrate the characteristics of the proposed control technique in terms of current tracking, ( $x-y$ ) currents reduction and THD of stator currents compared to the classic PCC.

A Novel Modulated Model Predictive Control Applied to Six-Phase Induction Motor Drives

Model predictive control method has been recently introduced as an alternative to inner current controllers of multiphase drives using rotor field oriented control methods Model predictive controllers are distinguished by a variable switching frequency which causes noise, large voltage and current ripples at low sampling frequency Therefore, this paper proposes a variable-speed control for six-phase induction motor drives by using an inner loop of predictive-fixed switching frequency current control scheme Experimental results are provided in order to prove the feasibility of the proposed control technique, considering mean squared error as well as the total harmonic distortion of the stator currents as figure of merit The efficiency of the proposed control could be verified by applying the nonparametric Mann-Whitney statistical test on the experimentally obtained data

Variable-Speed Control of a Six-Phase Induction Machine using Predictive-Fixed Switching Frequency Current Control Techniques

This paper presents a new finite control set model predictive control strategy that, contrary to conventional approaches, achieves (i) zero steady-state error in the converter’s AC current, and (ii) both fixed and lower harmonic spectrum, similar to that achieved by pulse width modulation based control schemes. These characteristics are attractive for medium and high voltage applications where high dv/dt is prohibitive and reduced switching losses are a must, or in applications that use passive filters and where a spread harmonic spectrum can cause resonances. The proposed strategy achieves dynamic results similar to those of conventional predictive control and a steady-state performance similar to that of a modulated control strategy. To do so, the strategy utilizes a modulated integral action to incorporate an input restriction into a conventional predictive control cost function. A grid-connected cascaded H-Bridge multilevel inverter is used to validate the strategy. Simulated and experimental results in both steady and transient states are presented to verify the proposed strategy’s performance in the converter.

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A Hybrid FCS-MPC With Low and Fixed Switching Frequency Without Steady-State Error Applied to a Grid-Connected CHB Inverter

Within a power converter, multiple currents are usually measured for control, protection, and/or monitoring. They are therefore important sources of information, which must unquestionably be measured accurately to maintain continuous and reliable operation of the power converter. Accurate current measurement has however become tougher with the introduction of wide band-gap (WBG) devices with switching frequency tending toward the megahertz (MHz) range. Because of that, the installed current sensors must have a significantly widened bandwidth. Moreover, they must be nonintrusive and compact, in order not to degrade fast switching characteristics and high power density of the WBG converter. Presently, these features are not collectively obtainable from existing commercial current sensors. Consequently, many new current sensing techniques have surfaced in the literature for usage with the more demanding MHz power converter. These new techniques, some classical techniques, and their hybrid integrations are now reviewed, after overviewing functionalities made possible by current sensors in a power converter. Last but importantly, some future developmental trends aimed at matching MHz current sensors with MHz power converters are described, before concluding the article.

https://ieeexplore.ieee.org/ielx7/63/9714885/09658157.pdf

A Review of Megahertz Current Sensors for Megahertz Power Converters

The absence of modulator in model based predictive control technique for different converter topologies generates a variable switching frequency that produces high frequency harmonics and higher stress on the power semiconductor devices. In this paper, a novel model based predictive control strategy with a fixed switching frequency applied to a three-phase cascade H-bridge multilevel STATCOM is introduced with the aim to increase the performance of classical model predictive control. Simulation results show increased performance of the proposed control method in terms of current waveform total harmonic distortion.

Model based predictive current control for a three-phase cascade H-bridge multilevel STATCOM operating at fixed switching frequency

There are several control techniques for active power filter applications. This paper presents a new alternative of predictive current control for a cascade H-bridge multilevel converter, where the optimal vector selected by the predictive controller is used for a modulation stage to obtain a fixed switching frequency. Simulation results validate the proposal where almost similar results can be obtained in comparison with the traditional methods.

A novel predictive-fixed switching frequency technique for a cascade H-bridge multilevel STATCOM

Finite-control-set model-based predictive current control (FCS-MPCC) technique is distinguished by a variable switching frequency which causes high harmonic distortion a low sampling frequency. This latter could be considered an undesired behavior for active power filter for grid-connected applications. To overcome this issue, this paper proposes a modulated FCS-MPCC applied to a three-phase four-wire active power filter based on H-bridge converter. Simulation results are developed to demonstrate the efficiency of the proposed modulated FCS-MPCC comparing with classic FCS-MPCC, thus concluding the advantages and limitations of each technique at transient and steady states.

Modulated Predictive Current Control Technique for a Three-Phase Four-Wire Active Power Filter based on H-bridge Two-Level Converter

In this paper, a scheme for reactive power compensation and neutral current elimination based on model predictive control strategy is proposed. In this context, a H-bridge four-wire two-level active power filter is presented. The main feature of the proposed method focuses on the compensation of reactive power and neutral current elimination for unbalanced load in order to improve the power factor. This approach predicts the future behavior of the control actions considering all possible switching states. The proposed method selects the optimal switching vector by using an optimization process considering a defined cost function. The effectiveness of the proposed control approach is evaluated through simulations.

Model predictive current control with neutral current elimination for H-bridge two-level active power filters

Despite all advantages of model predictive control, when this control scheme is implemented in power converters, like multilevel cascade H-bridge, it generates a variable switching frequency. This variable switching frequency can deteriorate the performance of the system. This paper examines this problem and proposes two different modulation stages to the model predictive control to solve this issue. A comparative analysis of this modulation stages with conventional predictive control, in terms of total harmonic distortion, reference tracking error, output voltages waveforms, and balance voltages on the capacitors with simulations results to validate the solutions are shown.

Julio Pacher

Papers

Model based predictive current control for a three-phase cascade H-bridge multilevel STATCOM operating at fixed switching frequency

A novel predictive-fixed switching frequency technique for a cascade H-bridge multilevel STATCOM

Modulated Predictive Current Control Technique for a Three-Phase Four-Wire Active Power Filter based on H-bridge Two-Level Converter

Model predictive current control with neutral current elimination for H-bridge two-level active power filters

Finite Control Set Model Predictive Control Strategies for a Three-Phase Seven-level Cascade H-Bridge DSTATCOM